Here's a list of common abbrevations and symbols that are easily found in Modern English:
- A. M. : Everyone knows what it means but not all people know what this stands for. It stands for "ante meridiem". The word 'ante' means 'before' and 'meridiem' means 'noon'.
 - e.g. : It stands for latin phrase 'exempli gratia', meaning 'for example'. Avoid this in writing a composition, write 'for example' or 'for instance' instead.
 - & : We know this symbol means 'and' but do we know how is this symbol called? It's called ampersand. Never use ampersand in a composition. It is used as a part of a name, title, or quotation.
 - etc. : This abbreviation stand for a Latin origin expression 'et cetera'. Use 'and so on' or 'and so forth' in a composition to replace the use of 'etc'.
 - et al : It is written after a list of names to mean that other people are also involved in something (for example in writing a book). For example: James Fitzgerald, et al.
 - ca. : It is pronounced 'circa' meaning 'about' or 'approximately', for example "The old church was built ca. 1800."
 - ibid : Sometimes it is also written out 'ibidem'. Usually 'ibid' is written in a formal writing to mean 'from the same book, writer, or article as the one that has just been mentioned'.
 - P. M. : It stands for "post meridiem" (after noon).
 - i.e. : It stands for "id est", a Latin term for "that is to say/ in other words".
 - a/c : You can find this on a check. This means 'account'.
 - ASAP : This stands for 'as soon as possible'.
 - BYO : It means 'bring your own'. When you're invited to a party or gathering, and the party is BYO, it means you have to bring your own food to eat there.
 - Ltd. : It stands for 'limited'.
 - RSVP :It is used on an invitation to request a response. It is derived from a French expression.
 - Bro./ Bros. : It stands for "brother/brothers". A family company usually uses this.
 - CV : It stands for 'curriculum vitae'. In American English, it is called 'resume'.
 - DIY : Do-it yourself (DIY) things can be done without anyone else's help.
 - est. : We can see this on some billboards belonging to some big and old companies. It stands for 'established'. The words 'est. 1912' means a company/ building was built in 1912.
 - HQ : It means 'headquarter'.
 - NB : It stands for 'nota bene'. It is usually written in the end of a letter, meaning 'take notice/note well'.
 - PS : It stands for a Latin expression 'post scriptum', meaning 'written after something'.
 - oz. : It is derived from 15 century Italian term 'onza'. It means 'ounce'. You are likely to see this on products' packages.
 - lb(s) : It is the written abbreviation of 'pound' in weight.